1. Field of the Invention
The present invention relates to communication systems. More particularly, the present invention relates to a system and method for communicating information signals utilizing dual low-noise amplifiers.
2. Background Information
In a conventional transceiver, such as, for example, a wireless transceiver, the received signal can be processed through a low-noise amplifier (LNA). The LNA amplifies very low-level received signals, while adding only minimal amounts of noise to the signal that can reduce receiver sensitivity. LNAs should be highly linear to handle weak signals in the presence of large interfering signals. Conventional transceivers use a single LNA. In transceiver systems that use multiple LNAs, the LNAs are not co-resident on a monolithic substrate, i.e., they reside on separate substrates.
FIG. 1 is a simplified diagram illustrating several components of a conventional transceiver 100 using a single LNA. The transceiver 100 includes a first antenna 105 and a second antenna 110 for transmitting and receiving signals. An antenna selection switch 115 selects either first antenna 105 or second antenna 110 for transmitting and receiving information. A radio frequency (RF) bandpass filter 120 eliminates large interfering signals outside the frequency band of interest from reaching the receiver components of the transceiver 100, and can be used to reject image frequency interferers that can have drastic effects on the receiver. The RF bandpass filter 120 generally spans the desired system bandwidth for communicating information. A transmit/receive switch 125 connects either the transmitter components or the receiver components of the transceiver 100 to either the first antenna 105 or the second antenna 110. For example, a transmitter 130 is used to transmit information. For received signals, a LNA 135 amplifies the low-level received signals, while adding only minimal amounts of noise to the received signal, before passing the amplified signal to a receiver 140.
The transceiver 100 can include numerous other components, such as a duplexer, mixer, intermediate frequency (IF) bandpass filter, automatic gain control, local oscillator, phase locked loop, power supplies, and the like. Using these and previously-described components, a RF wireless transceiver can receive a RF signal, down-convert the RF signal to an IF signal and the IF signal to a baseband signal, and demodulate the baseband signal. Various filtering and signal processing can be performed on the received signal during and between each of the various phases of down-conversion and demodulation to maximize the received signal and improve reception and receiver sensitivity. An exemplary wireless receiver is described in, for example, U.S. Pat. No. 5,963,856.
The signal applied to the lone LNA 135 can, however, suffer from loss associated with the antenna selection switch 115, the RF bandpass filter 120 and the transmit/receive switch 125. This loss, which can be, for example, as much as approximately 3 dB, adversely effects receiver sensitivity. In addition, these components add additional cost to the transceiver 100. The use of other LNAs located on separate substrates, with their concomitant switches and filters, can result in additional loss, as well as increased cost due to the greater number of components.